In the pharmaceutical field there are numerous medications which are administered in a liquid form. In many instances, these are administered by syringe. Although some types of medications may be packaged and stored in their liquid form there are certain medications which cannot be handled in this fashion due to stability problems. Thus, mixing vials have been provided for containing a dry component such as a powder in one compartment of a vial and a diluent in the other compartment. The two compartments are isolated from each other by a resilient rubber center seal. U.S. Pat. No. 2,908,274, Bujan, illustrates a conventional two-compartment mixing vial.
Mixing vials of this type may be stored for a fairly long period of time without encountering stability problems. When the contents of the vial are to be administered, the powder and diluent are mixed together within the vial and a syringe may be used to withdraw the newly constituted liquid. In the prior art the displacement of the center seal which isolates the two compartments from each other is effected by downwardly pushing a rubber plunger that seals the open end of the vial. This plunger, when pushed downwardly, acts as a piston and transmits force through the diluent in the upper compartment of the vial. The hydraulic pressure resulting from this action causes the center seal to become dislodged and fall into the bottom compartment of the vial. The liquid and powder then become intermixed and can be withdrawn by inserting a hollow needle through the plunger which is still positioned at the open end of the vial.
In such vials of the prior art, it is essential that the downward movement of the plunger which serves as a piston is somewhat restrained. U.S. Patent No. 3,087,638, Loper, teaches the use of a metallic ring which is positioned over the neck of the vial with upwardly extending pointed teeth for engaging the plunger thereby preventing the plunger from passing through the opening of the vial and into the medication. It is also apparent that in order to dislodge the center seal with the hydraulic pressure created by the downward movement of the plunger that the upper compartment must contain liquid. From a production standpoint, there are certain instances where it would be preferable to place the liquid in the lower compartment of the vial and then place powder in the upper compartment, an arrangement which would not provide full assurance of being able to displace the center seal.
In order to avoid these limitations that accompany the use of hydraulic pressure for displacing the center seal, various ideas have been developed with respect to mechanically displacing the center seal. U.S. Pat. No. 3,842,836, Ogle, has suggested the use of a probe or pointed rod that can be inserted through the plunger of the vial to reach and dislodge the center seal. While such a procedure would effectively dislodge the center seal, it creates additional production problems in that the probe that would accompany the vial would require a separate sterile package. Furthermore, the integrity of the sealed vial would be broken by the introduction of the "foreign" probe.
U.S. Pat. No. 2,689,566, Lockhart, discloses a plural compartment vial with a center seal which is dislodged by a hollow dropper rod. The rod and a flexible bulb enveloping its exterior end are removable for administering drops of the mixture. The bulb is subject to accidental actuation and also comes into direct contact with the fingers of the operator. Although such physical contact is not objectionable for administering drops there is a reluctance for this to occur if a sterile syringe needle is to pierce the bulb for removal of the medication.